Hip Dysplasia is a problem that is mainly genetic in origin, but the degree to which it affects dogs can be affected by other factors: food, environment, etc. It can affect any breed of dog (and sometimes cats) but is more common in the larger breeds, which grow faster. Males and females are equally susceptible.
Dog’s hips are, like ours, a ball & socket joint – with the rounded top of the thigh bone (the ball) fitting into a cup-shaped socket in the hip bone. This socket also contains some cartilage – this and nearby ligaments and muscles help to keep the hip joint working properly.
In the first couple of months of a dog’s life, the hip joints are still developing and are susceptible to unnatural stresses which can cause malformation of the joint. These stresses begin once the puppy starts to crawl & walk. The bones in the joints are usually hard enough and the leg muscles strong enough to resist malformation by the time the puppy is 6 months old. Before this time, if the stresses on the hip joint are too often greater than the muscles and ligaments can absorb, the soft bone of the joints will be affected, causing them to grow malformed.
A loose hip joint will also put stress on the cells which create the cartilage – which will lead to arthritis. Inflammatory cells will appear in the hip joints, cartilage will absorb water and swell; causing further malformation of the joints.
The onset and degree of hip dysplasia is often a result of overfeeding at an early age. Hip dysplasia is often seen in puppies who have gained weight too quickly in their first 2 months. It is important that puppies’ weight should be monitored to ensure they only grow to the correct weight for their age. A good diet should contain enough protein to allow correct development, not so much that the puppy starts to get fat.
Bones are primarily made of calcium and, in a growing puppy, most of the calcium in the diet will be used for bone growth. While it is tempting to think that a high-calcium diet will improve bone growth & strength, in practice it often leads to irregular growth – which in the hips will mean badly-fitting joints.
It is possible to treat hip dysplasia, by drugs and by surgery. However, drug treatments are only for the relief of pain and prevention of further damage.
As the puppy grows into an adult dog, it remains important to continue with a healthy diet to prevent obesity and minimise stress on the hip joints. While adult bones should not deform and cause hip dysplasia, excess weight will aggravate any arthritic tendencies developed as a puppy. In this situation, exercise needs to be carefully controlled; enough exercise is needed to keep the muscles strong, but too much will cause further injury to the joint. Swimming is usually recommended as good exercise for the leg muscles – without causing impact stresses on joints. Keeping the joints warm, or even mild heat treatment may help – it is thought that the warmth helps the muscles to relax, allowing better stretching of the muscles and greater freedom of movement.
There is a school of thought that Vitamin C supplements help to prevent hip dysplasia; the theory is that Vitamin C is necessary to build health cartilage and a deficiency in Vitamin C could lead to weak cartilage and hence loose joints. However, there is no medical evidence for this or that Vitamin C supplements are beneficial.
The pain caused by hip dysplasia is best treated with anti-inflammatory drugs (not the steroid kind). These would commonly be aspirin or phenylbutazone. If these are not effective, or the inflammation is severe, corticosteroids may be prescribed. This should only be undertaken cautiously as over-use of steroids brings the risk of a number of undesirable side effects.
Other treatments that may help in the treatment of hip dysplasia are polysulfated glycosaminoglycans, which is injected into the muscles and help to cushion the cartilage – hyaluronic acid, which is injected into the joints and acts as a lubricant – and Superoxide dismutase, which can be injected into the joint or under the skin and helps to stabilize the cell membranes of inflamed joints.
Surgical treatment of hip dysplasia depends on the severity of each case and ranges from surgery on muscle tendons to complete hip replacement in severe cases.
As originally stated susceptibility to hip dysplasia in dogs is mainly genetic and is inherited from the parents. As such, effective control of the disease can be achieved by preferring unaffected dogs for breeding. Many breeds of dogs are benefiting from this policy; between 1981 and 1988 19 breeds of dog out of 24 studied showed a decrease in their incidence of hip dysplasia, compared to the period 1972 to 1980. Only 1.8% of Borzois suffered from the disease, compared to 48% of St. Bernards.
Evaluation of a hip dysplasia problem requires an X-ray of the joints – from the lower back to the knee. The dog needs to be sedated for this. Evaluation of an X-ray may be affected by the age of the dog, its level of exercise, being anesthetised or if a bitch is in season. A dog under a general anaesthetic may appear to have looser hips than it does when awake. A “season” may also give indications that the hips are looser than they really are. The hips may also be slightly loose if the dog has not been regularly exercised.
Early evaluation of a young dog’s hips is very useful in determining the dog’s vulnerability to hip dysplasia. Studies have shown that the results of tests done on dogs under 2 years old were rarely contradicted when the tests were repeated when the dogs were older.
The most effective way of reducing the number of dogs who suffer from hip dysplasia is for breeders to take responsibility for getting all potential sires & dams checked before breeding from them. If only dogs who are clear of this disease are bred, the incidence of hip dysplasia can be effectively decreased.